Mining tunneling operations typically include a tunnel boring machine which cuts and fractures the rock and produces muck material. A transfer conveyor is towed by the tunnel boring machine. The transfer conveyor removes the muck material from the tunnel boring machine and usually conveys the muck material up and over to one side of the tunnel. The muck material is discharged to a receiving hopper of an advancing tailpiece which is also towed by the tunnel boring machine. The muck material is then loaded onto a continuous belt conveyor.
The support structure of the continuous belt conveyor is secured to the tunnel. However, the continuous belt conveyor must extend or advance with the advancing tunnel boring machine. The advancing tailpiece makes possible the advancing of the continuous belt conveyor. The advancing tailpiece is usually supported by one of the vehicles which is towed by the tunnel boring machine. The end loop of the belt is carried by a pulley of the advancing tailpiece. As the advancing tailpiece advances, the belt length gets longer as it is pulled out of a belt storage system, typically near the discharge end of the belt conveyor. The belt storage system is usually a cluster of pulleys which can be moved to allow the continuous belt conveyor to extend.
As the advancing tailpiece advances, the distance increases between the support structure of the conveyor and the pulley of the tailpiece, as well as the belt spanning therebetween. As the advancing tailpiece advances, return rolls are secured to the continuous belt conveyor system. The return rolls support the belt during the belt return path at the bottom of the continuous belt conveyor. Carrying idler assemblies must also be installed within the loop of the belt to support the belt during the load carrying portion of the path of the belt. The carrier idler assemblies must be installed through the frame of the tailpiece. The carrying idler assemblies are installed by workers on a frame of the continuous belt conveyor, typically using J-bolt/loop-nut arrangements. The carrying idler assemblies and return rolls form the support structure of the continuous belt conveyor. The carrying idler assemblies do not move with the advancing tailpiece and so they must be installed prior to the advancing tailpiece advancing beyond the distance the belt can be supported by the last installed carrying idler assembly and the advancing tailpiece.
To accommodate the worker, the frame of the tailpiece must include an access opening for the worker to climb into the advancing tailpiece to install the carrying idler assembly. The tailpiece typically includes 3 or 4 belt pulleys such as shown in U.S. Pat. No. 4,890,720. The number of pulleys, in part, dictates the size of the advancing tailpiece. The larger the tailpiece, the less space is available in the tunnel adjacent the tailpiece. This is an important consideration because in small bore diameter tunnels, for example, 10 foot to 11 foot diameter, the area where the advancing tailpiece is located becomes very congested as tunnel supply trains must pass by the advancing tailpiece, and due to other tunneling operation support functions that must be carried out in this area such as ventilation, dust collection, water pumps, electrical transformers, and tunnel structural support erection equipment.
The tow vehicle typically rides on steel rails or slides on skid rails and is towed by the mining machine. The movement of this vehicle as it is towed will not be an accurate line, therefore, in order to keep the advancing tailpiece located accurately on the belt centerline, there must be some method of moving the advancing tailpiece relative to the support car.
This is accomplished in the prior art with two horizontal extension booms to provide for lateral movement, two vertical tracks to provide vertical movement and two tilt cylinders to control the roll of the tailpiece about a longitudinal axis.